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 2006 G. Chastain

Navy Ship Compartment Numbering

This material was extracted from the US Navy's Damage Control Training Department's Curriculum Unit Description at the Surface Warfare Officer's School Command.  

For description of Navy Ship Terminology, see Glossary of Nautical Terms.

Compartments are numbered for identification to facilitate location. The identification number assigned locates each compartment specifically, and generally indicates the function and use of the compartment. Compartment numbers consist of four parts, separated by hyphens, for example 6-150-0-E, in the following sequence:

  1. Deck Number
  2. Frame Number
  3. Position in relation to centerline of ship
  4. Compartment use
Deck Number: The main deck is the basis for this numbering scheme and is numbered 1. The first deck below the main deck is numbered 2, and so on. The first horizontal division above the main deck is numbered 01, and the numbers continue consecutively for subsequent upper division boundaries. Compartments are numbered by the lowest deck within the space.

Frame number: The forward perpendicular is the basis for this numbering scheme and is numbered "0" (zero). "Frames" are consecutively numbered, based on frame spacing, until the aft perpendicular is reached. Forward of the forward perpendicular, frames are "lettered" starting from the perpendicular to the bull nose (A, B, C, etc.) while frames aft of the after perpendicular are "double lettered" to the transom (AA, BB, CC, etc.). Compartments are numbered by the frame number of the foremost bulkhead of the compartment. If this bulkhead is located between "frames," the number of the foremost "frame" within the compartment is used. Fractional numbers are not used except where frame spacing exceeds four feet. 

Frame spacing examples:
CG/DD/DDG/FFG     12IN   LHD/LHA     7FT
LSD  4FT    CVN  4FT
LPD  2FT Cutters  1FT
Want to know what all of these letters mean?  These are the ship classifications and the Navy provides a list of the current usage.

Position in relation to centerline: The ship's centerline is the basis for this numbering scheme. Compartments located so that the centerline of the ship passes through them are assigned the number 0. Compartments located completely to starboard of the centerline are given odd numbers, and those to port of centerline are given even numbers. The first compartment outboard of the centerline to starboard is 1, the second is 3 and so forth. Similarly, the first compartment outboard the centerline to port is 2, the second is 4 and so forth. There may be cases in which the centerline of the ship would pass through more than one compartment, all of which may have the same forward bulkhead number. Whenever this occurs, that compartment having the portion of the forward bulkhead through which the centerline of the ship passes is assigned the number 0 and the other carry numbers 01, 02, 03 etc.

Compartment Use: A capital letter is used to identify the assigned primary use of the compartment. Only one capital letter is assigned, except that on dry and liquid cargo ships a double letter identification is used to designate compartments assigned to carry cargo. Examples of compartment use are storage areas, various tanks, and living quarters. 

Some examples from NSTM 079 volume 2:
A Storage area
C Ship and Fire Control operating spaces normally manned
E Machinery spaces which are normally manned
F Fuel or Fuel Oil tanks
J JP-5 tank
L Living quarters
M Ammunition (stowage and handling)
Q Areas not otherwise covered
T Vertical access trunk
V Void

Example of Compartment Numbering

Given Compartment "6 - 150 - 0 - E," we can determine that it is located:

a) five decks below the Main Deck,
b) foremost bulkhead is at frame 150,
c) centered upon the centerline of the ship, and
d) is used as an engineering space.

Figure 1 illustrates how compartments are numbered throughout a ship.

Compartments.gif (8990 bytes)

Click To Enlarge